In vitro comparison of oxygen availability from asanguinous and sanguinous cardioplegic media.

Repayment of oxygen debt by periodic reperfusion of the ischemic myocardium is determined in part by the oxygen deliverability of the infusate. Total oxygen content of the infusate may not reflect what is available to the tissue. Available oxygen was measured at 10 degrees C and 20 degrees C by equilibrating 0.05 ml of infusate with 2.85 ml of deoxygenated normal saline; an oxygen electrode quantitated its release into the saline. Sanguinous cardioplegic media at 10 degrees C released 2.41 +/- 0.15 ml O2/100 ml, representing only 37--38% of their total oxygen content, and 3.12 +/- 0.17 ml O2/100 ml at 20 degrees C, representing 50% of their total content. Oxygenated asanguinous media released 4.06 +/- 0.10 ml O2/100 ml at 10 degrees C and 4.00 +/- 0.09 at 20 degrees C, representing their total oxygen content. Thus, oxygenated crystalloid media can deliver as much oxygen as sanguinous media at these low temperatures.